ByChristopher Torchia, Associated PressDecember 3, 2015

Judge Eric Leach delivers his judgement in the Oscar Pistorius case in the Supreme Court of Appeal in Bloemfontein, South Africa, December 3, 2015. Paralympian Pistorius' conviction for killing his girlfriend Reeva Steenkamp has been scaled up to murder from culpable homicide by South Africa's top appeals court.

Johannesburg, South Africa — A South African appeals court on Thursday convicted Oscar Pistorius of murder, overturning a lower court's conviction of the double-amputee Olympian on the lesser charge of manslaughter for shooting girlfriend Reeva Steenkamp to death in 2013.

Justice Lorimer Eric Leach of the Supreme Court of Appeal delivered the ruling by the five-judge tribunal in Bloemfontein and directed the trial court, the North Gauteng High Court, to impose sentence. He did not specify when that should happen. The former track star is currently under house arrest at his uncle’s mansion in Pretoria.

“The accused ought to have been found guilty of murder on the basis that he had fired the fatal shots with criminal intent,” Leach said to the courtroom, in which Steenkamp’s mother sat.

Pistorius was placed under house arrest in October after serving one year in prison. He had been sentenced to five years in prison for manslaughter and got out early in line with corrections department regulations. The trial court can also consider whether he should be shown leniency because he is disabled and is a first-time offender.

Pistorius, 29, killed Steenkamp in the early morning of Valentine’s Day. He insisted he thought she was an intruder behind the door of a toilet cubicle in his home. The prosecution said Pistorius shot Steenkamp during an argument.

Leach said regardless of who might have been behind the door, Pistorius should have known someone could be killed if he fired.

"The identity of his victim is irrelevant to his guilt," the judge said.

Under the concept of "dolus eventualis" in South African law, a person can be convicted of murder if they foresaw the possibility of someone dying through their actions and went ahead anyway.

Reeva Steenkamp's mother, June, sat quietly in the courtroom during the announcement, which was shown live on television. Pistorius was not there.

Reeva Steenkamp's father, Barry, told South African television channel ANN7 that he was relieved by the judgment and described it as fair.

"Let us now all get on with our lives," Barry Steenkamp said. His voice breaking with emotion, he said of his daughter: "I'm sure she'll be able to rest as well now."

The Pistorius family said in a statement that it had taken note of the judgment.

“The legal team will study the finding and we will be guided by them in terms of options going forward,” the statement said.

A date for the former athlete’s new sentencing will be announced in the city of Pretoria, where he had been tried and imprisoned.

On Tuesday, journalists got a look at his former cell during a tour of a maximum security prison. It is in the hospital section of the Kgosi Mampuru II prison and is furnished with a single mattress on a metal frame, a basin with a backdrop of white tiles on the wall and a small cabinet. A barred window is backed by a metal screen, blocking the view.

The austere cell is set apart from the main prison in an area with a room for just one other inmate.

Pistorius, a multiple Paralympic champion, became one of the world's most famous athletes and the first amputee to run at the Olympics and the able-bodied world championships. He was known as "Blade Runner" for his carbon-fiber running blades

Leach described the story of Pistorius and Steenkamp as a “human tragedy of Shakespearean proportions" whose legal aftermath was conducted in the glare of international attention.

"A young man overcomes huge physical disabilities to reach Olympian heights as an athlete,” Leach said. “In doing so he becomes an international celebrity. He meets a young woman of great natural beauty and a successful model. Romance blossoms and then ironically, on Valentine’s Day, all is destroyed when he takes her life.”